A film of TiO2 is sometimes formed on a substrate such as a Si wafer by plasma-enhanced atomic layer deposition (PE-ALD) using tetrakis (dimethylamido) titanium (TDMAT) and O2. In order to achieve desired film quality, only high frequency power is sometimes made higher, or only an application time of high frequency power is sometimes made longer, without change in film formation conditions such as the amount of feed of a material gas (source) for film formation, a time for the feed, and a source purge time. For example, the high frequency power is made higher, or the application time of high frequency power is made longer when forming a film with film quality of a low etching rate. In such a case, a TiO2 film is formed which has a film thickness profile in which the film thickness is extremely thicker on the outer portion of the substrate than on the inner portion thereof, which causes poor in-plane film thickness uniformity although the desired film quality can be obtained. The outer portion of the substrate is an annular portion along the outer edge of the substrate, and the inner portion thereof is a portion including the center of the substrate and enclosed by the outer portion.
It is presumed that the film thickness on the outer portion of the substrate increases due to plasma spreading to the periphery of the outer portion of the substrate and due to the field intensity of the plasma increasing in the periphery of the outer portion when strong high frequency power is applied.
In order to adjust the film thickness distribution in the plane of the substrate while achieving the desired film quality, there can be needed complicated adjustment of film formation conditions such as the amount of feed of material gas, the flow rate of reactant gas, the flow rate of carrier gas, a pressure in the chamber in film formation, the distance between electrodes, and the temperature of the substrate. For example, the film thickness in the plane of the substrate is intended to be uniform. Change to dedicated hardware used under the conditions for strong high frequency power is considered when it is unable to adjust the film thickness distribution while achieving the desired film quality under adjustment of the film formation conditions. The change to such hardware increases costs.